Modern engine assemblies, including but not limited to diesel engines, may include a direct injection fuel system having a fuel injector that directly injects a stream of fuel, i.e., a fuel spray, into a combustion chamber of the engine assembly. The fuel spray mixes with air within the combustion chamber prior to combustion. The degree of mixture achieved between the fuel spray and the air within the combustion chamber affects the fuel economy and the hydrocarbon emissions of the internal combustion engine.